Posts referring to the Panasonic PT-D3500U

I work for a small sound company that occasionally installs projectors/AV equipment in commercial markets. I recently acquired the responsibility of taking care of this aspect of the company's work. So I'm quoting a projector for a church that wants to throw 80 feet and achieve a 110 inch screen size (diagonal). They have an older Ekei lcx-990 that according to the specs will throw up to 48.6 feet with a screen size as small as 308 inches. But by manually adjusting the focus (unscrewing the lens) it will throw 80 feet with a much smaller screen size. I think it's the standard lens, and not a long-throw lens... but this indicates that the specs are not a very accurate limit of what one can do with the projector. Is this the case with most projectors? I understand that there can be compromises in quality by exceeding these "specs" but are they ever/sometimes/always really limits, or just guidelines? Another basic question this leads up to is: is there a difference between the terms "focus" and "zoom?" and do all larger (permanent install) projectors have a manual focus/zoom capability (turning the lens clockwise or counter-clockwise)? I'm wondering if the Panasonic PT-D3500u will do the trick. Any comments would be greatly appreciated!